Monasticism developed from the ancient practice of eremeticism, or isolating oneself from the “civilized” world. Hermits would isolate themselves in the “wilderness” to be closer to God and battle with their inner demons. Anthony of Egypt was an influential hermit who lived for 105 years, fighting demons in the wilderness for much of his life. From eremeticism developed monasticism to oversee the spiritual needs of the hermits. A main purpose of eremeticism and monasticism was to maintain an ascetic lifestyle and appealed to both men and women. Those who lived a monastic lifestyle removed themselves from the comforts and temptations of the world. Communities of those wishing to renounce the world and dedicate themselves to the contemplation of God formed first in Egypt in the 300s. The goal of these single-sex communities was to be self-sufficient so as to have limited contact with the outside world. The depravity of an ascetic life was to encourage a closer connection to God and to allow a greater focus on spiritual duties. Monasticism spread from the east into Italy and southern Gaul in the fifth century.

The Monastery of Lérins was founded in 410 CE as a training center for bishops that combined Egyptian severity with an intellectual dimension. By the beginning of the sixth century, monasticism had gained wide support throughout Europe with many monasteries being constructed in the north by newly converted Irish Christians. In Italy, Benedict of Nursia (c. 480-553) founded the monastery of Monte Cassino and established a code for the conduct and daily life for those in monastic communities, which became known as the Benedictine Rule. It consisted of daily prayer at regulated intervals, manual labor, and scriptural study. In Benedictine communities the abbot had complete control but he was mandated to consider what the members of the community had to say. Other monastic rules followed, the Rule of St. Columba of Iona among them. Monastic rule generally allowed only a very strict, severe lifestyle with allotments for prayer, work, and scholastic pursuits. In Ireland, the monastery developed as the center of Christian society rather than the bishops as on the continent. The monasteries of Ireland became major centers of learned culture as well as spiritual centers. Literacy was especially important for the continued spread of Christianity.

The self-sufficiency and self-governance of monasteries made them potential rivals of the Church hierarchy. The special status monks had inspired bequests and gifts from the wealthy in the region, bolstering the influence and prestige of individual monasteries. Bishops, who had little say in the operation of monasteries in this early period, often believed this undercut his authority and the influence of local churches. On the continent, the Germanic kings were establishing royal monasteries for unwed family members and political opponents. These monasteries fell under the protection of the royal family, but could fall out of favor quickly if the exchange of fiscal “gifts” to the monastery were not returned by spiritual blessings. These continental monasteries organized the surrounding territory and residents for the kings in return for financial support and land. With the accumulation of land, the monasteries were able to gain a semblance of financial independence rather than relying solely on the generosity of the kings. The kings also granted the monasteries immunities from royal taxes and law. With the acquisition of land and resources, the monasteries became important economically as centers of trade.

Throughout much of the medieval era, the clergy remained one of the few literate parts of society. Much time went into the production of illuminated manuscripts, ornately decorated religious texts written in Latin

As well as economic importance, monasteries became centers of scholarship and culture. Books were produced at many monasteries, spreading ideas around Europe and educating the upper classes that sent children to learn at the monastery. In Ireland, a penitential discipline developed that regularized the penance system throughout Europe. However, by the eighth century, monastic reform had begun in Carolingian France. The Monastery of St. Gall was rebuilt in 818 CE as the model of an ideal Carolingian monastery. In 910 CE, the most important monastery of the Middle Ages was constructed at Cluny. Cluny was chartered as a completely independent monastery with no secular or Church authority above it. Cluny became a major component of monastic reform, establishing a monastical empire as its monks replaced the abbots of corrupt monasteries throughout Europe. In the era of feudal mutation, Cluny remained a source of continuity for the Frankish world and provided a nucleus of stability. The idea of a prayer confraternity was also developed at Cluny, allying it with powerful nobles and kings in the disintegrating Frankish Empire. The power of Cluny as an economic, political, scholastical, and spiritual institution marked the height of monasticism in Europe. The power of the monastery had never been greater before Cluny, and monastical power began to wane during the Middle Ages as powerful warlords and kings rose to power across Europe.

Another wave of monastic reform spread during the eleventh century. This reform sought to return to a simpler monastic lifestyle, one characterized by poverty, which stood in contrast to the perceived lavishness of monasteries such as Cluny. The Carthusians were one such group of reformers. Founded in the 1080s by Bruno of Cologne, Carthusian communities were small and members took vows of silence, slept apart in individual cells, and spent their days in prayer and meditation. Another reformed order, the Cistertians, also sought a life of simplicity and poverty. Led by St. Bernard (c. 1090-1153), the Cistertians upheld the Benedictine Rule, maintained unadorned churches, spent their days in private prayer. They also carefully maintained and managed monastic estates to ensure self-sufficiency, wore simple, undyed robes, and celebrated a simplified communal liturgy. they emphasized personal emotion in spirituality, highlighting the humanity of Christ and the Virgin Mary.

In the late twelfth century a new type of religious order appeared, one whose members did not isolate themselves but rather wandered through towns and cities preaching and tending to the poor. They were friars ("brothers") and distinguished themselves from monks by relinquishing all worldly possession and means to support themselves with food and shelter. Instead they begged as they wandered and traveled to locations by papal directive. They are known as Mendicant Orders (mendicare means "to beg"). The first of these orders was established by a Spaniard named Dominic (1170-1221). His order, called the Dominicans, was dedicated to combating heresy and converting non-Christians to the faith. They did this through persuasion and argument, which meant thorough study of scripture, theology, and papal decrees. As a result, the Dominicans went through training in languages, theology, and philosophy, all directed by the Dominican Order itself. The second Mendicant Order to receive papal approval was the Franciscans. Founded by Francis of Assisi (1182-1226), the son of a wealthy merchant who renounced his inheritance in order to serve the poor, the Franciscans preached repentance and tended to the outcasts of society. They relied on the charity of those to whom they preached and served. Inspired by Francis, one of his early followers, a noblewoman named Clare formed a group of pious women who sought to work alongside the friars. The presence of women in the streets, however, elicited disapproval from both the papacy and Francis and the order that would become the Order of the Sisters of St. Francis were cloistered in a traditional female monastic house.